I have now done 68 chests on the same Joint Operation, without an SSR Matrix.. so it's not a hard pity
I have opened a total of 181 chests so far.. and logged all of them so far... my last SSR Matrix was on chest 109, and I've done 68 chests on Spacetime Training Ground VII.
That means 68 is not a hard pity for SSR Matrix, also i have no more VIT so i'll probably update this on Friday, when I can do the same dungeon again.
Also, all 181 chests have been the 3rd chest on the dungeon, the one after the final boss. And no, I'm not counting the vehicle pieces chest
Worth mentioning that SR Matrix pity can go as far as 18 chests.. all in the same dungeon
Yellow gear pity is 7.. but the 6th chest has a HUGE increase in rate, so most people think it's the 6th. This pity does not reset if u get a yellow in between. Purple gear will reset the pity, but that's only 3 chests so nobody cares.
Edit: Sharing my notes ( Keep in mind I will still use it as a notepad )... Ignore the first 30 chests, I was logging them, but I didn't keep track of SRs https://docs.google.com/spreadsheets/d/1JcDds63yU8QOnaksYs83h2fk6FiHfm8g1mXjUdCMDxU/edit?usp=sharing
Edit2: per request, updated my progress in this post https://www.reddit.com/r/TowerofFantasy/comments/xrreu2/ssr_matrix_on_my_73rd_chest_87_overall_meaning/